The present invention relates to a trailing edge flap extension mechanism for increasing the overall planform area of the main wing of an aircraft. More particularly, the invention pertains to a cam track guided angle-of-incidence means for increasing the overall wing airfoil camber whereby the overall lifting capability or coefficient of lift of the wing may be increased during the take-off or landing modes of the aircraft.
As evidenced by U.S. Pat. No. 4,605,187, issued Aug. 12, 1986, to Stephenson, considerable development effort has been applied to find ways to support both the leading edge and the trailing edge flap mechanisms internally of the wing airfoil envelope. The Stephenson invention eliminates the aerodynamic drag penalty associated with large fairings usually required for housing the leading edge and the trailing edge flap support structure and drive mechanisms.
With the advent of increasingly higher aspect ratio wings and thinner wing airfoil sections, problems are encountered in using an internal arrangement for mounting the support and operating mechanisms of both the leading edge and the trailing edge flap systems. These higher aspect ratio wing designs also require relatively powerful high-lift devices for slow speed flight, e.g., the landing or take-off mode of airplane operation. However, the wings no longer have the necessary internal volume for completely containing the actuation and drive mechanisms for the high-lift devices. Further, in order to avoid excessive wing flutter in these latest high aspect ratio wing designs, both their stiffness and strength have to be increased. The strength and stiffness can be substantially increased by increasing the chord width of the structural wing box. Thus, it is very important to locate the wing box spars as far apart as possible while still retaining adequately sized flaps. If the space allotted for flaps and their associated support is too great, then the strength and stiffness can only be increased by substantially increasing the thickness of the upper and lower wing panels and the front and rear spar webs. However, these methods result in significant weight penalties.
The present invention is directed towards those airplane designs incorporating high aspect ratio wings having relatively thin airfoil sections with spanwise bending flexibility. More particularly, the present invention provides both an improved structural wing box and an improved external support mounting and operating mechanism for the high-lift systems.
With respect to a preferred embodiment of the invention relating to a wing trailing edge flap system, the external support mounting comprises a cantilever beam which is fixedly attached to wing structure. The cantilever beam provides for a relatively long travel of the trailing edge flap in combination with a good functional positioning operation of the flap elements. This is achieved by an extension and retraction mechanism through its overall travel range of actuated positions, i.e., the extension function of the mechanism accomplishes a good rearward projection and rotation of the flap elements relative to the main wing chord plane.
The wing trailing edge flap system incorporates a dual carriage flap support mechanism and a ball screw actuation mechanism for extension/retraction operation of the trailing edge flap elements. The dual carriage comprises a fore-carriage and an aft-carriage articulatably connected thereto. The fore-carriage is actuated by a ball screw drive mechanism and the aft-carriage has a double-slotted flap mounted thereon. Both the fore and the aft-carriages are individually roller-supported on separate cam tracks which are integral with and positioned on either side of a cantilever support beam fixedly attached to the main wing structure.
A streamlined fairing covers the entire dual carriage support and ball screw actuation mechanism.